The Mariners will be turning to one of the best prospects in baseball to help with the rotation as the team will be calling up right hander George Kirby to make his MLB debut this weekend.

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Seattle is in need of a fifth starting pitcher after the team demoted rookie Matt Brash after he struggled mightily to begin the 2022 season. Brash not only was optioned to Triple-A Tacoma, but he will begin a move to the bullpen, potentially for the rest of the season.

Kirby is starting Sunday against the Tampa Bay Rays, manager Scott Servais announced Saturday morning. That is notable because Brash’s next turn in the rotation was scheduled for Monday against the Philadelphia Phillies. As a result, Chris Flexen will pitch Monday instead of Sunday as initially scheduled.

Kirby, 24, is Baseball America’s No. 11 prospect in baseball and MLB Pipeline’s No. 30 prospect. Baseball America rates Kirby as Seattle’s No. 2 prospect while he’s No. 3 on MLB Pipeline’s list for the Mariners.

Kirby was the 20th overall pick in the 2019 MLB Draft after a standout collegiate career for Elon University, where he showcased elite command, striking out 107 batters while walking just six over 88 1/3 innings during his junior season.

The young right hander pitched just 23 innings as a pro in 2019, striking out 25 while not walking any batters. But due to the COVID-19 pandemic, Kirby was relegated to Seattle’s alternative training site for year as there was no minor league season.

With reports of increased velocity and better secondary offerings, Kirby started to shoot up prospect ranking lists ahead of the 2021 season.

In 2021, Kirby backed up those rankings by pitching very well between High-A Everett and Double-A Arkansas. Overall, Kirby pitched 67 2/3 innings in 2021 with a 2.53 ERA and striking out 80 to 15 walks.

Kirby entered 2022 spring training as one of three top candidates for Seattle’s fifth starting spot along with Brash and Justus Sheffield. Brash won out after a stellar spring while Kirby posted a 7.04 ERA in three appearances and started the year in Double-A.

While with the Travelers, Kirby has made five starts and has compiled 24 2/3 innings while posting a 1.82 ERA and striking out 32 to just five walks. You can see some highlights from a recent start at this link.

Baseball America and MLB Pipeline give Kirby a 70 grade on the 20-80 scale (50 being average) for his fastball, which sits in the mid-to-high 90s and can touch triple digits. Both sites give him excellent grades for his control as well. Pipeline grades Kirby’s control at well above-average at 65 while Baseball America gives Kirby a top-of-the-scale 80 grade for his command.

In addition to his excellent fastball and command, Kirby throws a slider, changeup and curveball. Baseball America rates the slider as a plus pitch with a 60 grade while giving his curveball an above-average 55 grade and his changeup an average 50 grade. MLB Pipeline rates all three of Kirby’s secondary offerings as above average at 55.

Other Mariners news

Catcher Tom Murphy left Friday’s loss to the Rays with a dislocated left shoulder and he was placed on the 10-day injured list Saturday morning. Taking his place is fellow catcher Cal Raleigh, who was demoted recently after struggling at the MLB level to start the year. Raleigh hit .286 with three extra-base hits in eight games in Triple-A, including four multi-hit games over Tacoma’s last five games.

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